UNIVERSITY    OF    CALIFORNIA     AGRICULTURAL    EXPERIMENT   STATION 

*w*a  ■  w~w    ~.r-     .__.._...._....-  BENJ.   IDE    WHEELER,    President 

COLLEGE   OF  AGRICULTURE  THOMAS  fqrsyth  hunj    ,_  ano  ,__ 

BERKELEY  h.  e.  van  norman,  vice-director  and  dean 

University  Farm  School 

CIRCULAR  No.  179 
October,  1917 

FACTORS  OF  IMPORTANCE  IN  PRODUCING 
MILK  OF  LOW  BACTERIAL  COUNT 

By  C.  L.  EOADHOUSE 


Galvanized-iron  sterilizing  tank  for  dairy  utensils. 

Since  the  keeping  quality  of  milk  is  greatly  influenced  by  the 
presence  of  bacteria,  a  study  of  the  sources  of  these  organisms  in 
dairies  and  the  practical  methods  of  limiting  their  numbers  in  milk 
is  of  great  importance  to  all  dairjrmen  and  more  especially  to  those 
engaged  in  producing  or  distributing  market  milk. 


Many  city  health  departments  in  carrying  out  the  provisions  of 
the  new  state  dairy  law  are  enforcing  the  grading  of  milk  and,  in 
order  that  dairymen  may  sell  the  higher  grades,  it  is  required  among 
other  things  that  the  number  of  bacteria  be  kept  within  certain  limits. 
It  is  the  purpose  of  this  circular  to  point  out  briefly  the  principal 
sources  of  these  organisms  and  to  explain  the  care  of  milk  which 
leads  to  a  lower  bacteria  content. 


BACTERIA  AND  THEIR  SOURCES 

Bacteria  are  microscopic  single-celled  organisms,  varying  in  size 
and  shape,  and  are  present  everywhere  in  nature.  Normally  the 
common  bacteria  in  limited  numbers  are  not  injurious,  but  when  they 
gain  entrance  to  milk  under  favorable  conditions  they  grow  rapidly; 
therefore,  in  a  few  hours  they  may  seriously  interfere  with  its  quality 
as  food  and  consequently  decrease  its  commercial  value.  Bacteria 
in  milk  originate  principally  from  the  interior  of  the  cow's  udder, 
body  of  cow,  the  milker,  milking  stable  and  utensils. 

INTERIOR  OF  THE  COW 'S  UDDER 

Bacteria  exist  in  the  udders  of  all  cows,  the  number  varying  in 
different  animals.  An  examination  of  1230  samples  of  milk  direct 
from  the  udders  of  seventy-eight  cows  at  the  New  York  Agricultural 
Experiment  Station  showed  an  average  of  428  bacteria  per  cubic 
centimer.  It  is  believed  that  organisms  gain  entrance  to  the  udder 
through  the  orifice  of  the  teat  and  that  they  are  sufficiently  numerous 
in  all  udders  so  that  it  is  not  possible  to  draw  any  but  minute  quan- 
tities of  milk  directly  from  the  udder  which  are  free  from  bacteria. 
Nothing  can  be  done  to  lessen  the  bacteria  content  of  the  normal  udder 
except  to  keep  cows  out  of  deep  mud,  particularly  the  mud  of  the 
stable  yard.  This  is  usually  permeated  with  manure  bacteria  and 
irritating  material  which  encourages  udder  trouble  and  the  subsequent 
increased  number  of  bacteria  which  frequently  accompany  such  con- 
ditions. 

Animals  which  have  apparently  recovered  from  previous  attacks 
of  udder  trouble,  in  some  instances,  yield  milk  with  an  enormous 
number  of  bacteria.  Milk  from  such  animals  if  mixed  with  the  milk 
from  the  remainder  of  the  herd  may  increase  the  average  bacteria 

We  desire  to  acknowledge  our  indebtedness  to  Mr.  F.  H.  Bothell  of  Los 
Angelefl  and  Dr.  G.  H.  Hart,  formerly  of  the  Los  Angeles  Health  Department, 
for  in  formation  pertaining  to  the  use  of  galvanized-iron  sterilizers. — C.  L.  R. 


content  to  a  marked  extent.  Bacteria  from  this  source  are  us  lally 
of  less  importance  in  clean  milk  production  than  the  other  soum  s  of 
bacteria  which  are  to  be  mentioned. 

THE  BODY  OF  THE  COW  GREATEST  SOURCE  OF  DIRT  IN  MILK 

The  skin  of  the  cow  is  one  of  the  important  sources  of  the  bacteria 
causing  souring  of  milk.  On  account  of  her  thick  coat  of  hair  and 
the  fact  that  she 'frequently  is  permitted  to  lie  in  a  dusty,  muddy  or 
manure-covered  corral,  a  great  deal  of  dirt  and  dust  laden  with 
bacteria  are  enmeshed  in  and  clinging  to  the  hair  of  the  animal's  body 
to  be  readily  dislodged  and  dropped  into  the  pail  during  the  milking 
process.  Good  dairy  practice  includes  the  washing  of  the  udder  and 
teats  before  milking  by  the  aid  of  a  hose  when  filth  is  present  and  the 
wiping  of  the  udder  with  a  damp  cloth  at  other  times,  whether  visible 
dirt  is  present  or  not.  As  a  means  of  lessening  the  dirt  and  bacteria 
gaining  access  to  milk  from  the  exterior  of  the  animal  the  use  of 
a  small-top  milk  pail  is  of  great  assistance  since  more  than  one-half 
of  .the  contamination  that  milk  receives  during  the  milking  process 
can  be  avoided  by  the  use  of  this  type  of  pail. 

Where  milking  machines  are  used  the  greater  part  of  the  contam- 
ination of  milk  from  the  body  of  the  cow  and  the  stable  is  eliminated, 
but  unless  great  care  is  used  to  thoroughly  wash,  brush  and  scald  tin? 
teat  cups  and  rubber  connections  after  each  using  and  to  keep  them 
in  a  chlorine  or  brine  solution,  or  other  acceptable  mild  antiseptic, 
the  bacteria  content  of  the  milk  may  be  higher  than  where  hand  milk- 
ing is  practiced.  A  careful  operator,  with  proper  knowledge,  who 
personally  attends  to  the  washing  and  care  of  the  milking-machine 
parts  may  consistently  produce  milk  with  a  low  number  of  bacteria. 

THE  MILKER 

The  milker  may  become  an  important  source  of  contamination  of 
milk,  particularly  if  he  is  not  clean  about  his  person.  His  hands 
and  clothing  may  give  off  a  great  many  bacteria  to  milk,  especially 
if  he  has  been  handling  the  feed  and  doing  farm  work  preceding 
milking  and  has  failed  to  wash  his  hands  thoroughly  and  put  on  a 
clean  milking  suit  before  starting  to  milk.  He  should  be  furnished 
with  clean  bedding,  facilities  for  bathing  and  encouraged  in  all  mat- 
ters of  personal  cleanliness.  The  milker  should  be  healthy  and  should 
discontinue  milking  at  any  time  a  member  of  his  family  or  household 
should  be  suspected  of  having  an  infectious  disease.  Wet  milking 
should  not  be  practiced  and  there  should  be  facilities  in  every  milking 
stable  for  milkers  to  wash  their  hands. 


THE  MILKING  STABLE 

The  construction  of  the  milking  stable  is  of  some  importance  in 
clean  milk  production  since  the  ledges  resulting  from  a  great  amount 
of  scaffolding  in  the  building  leave  a  place  for  dust,  dirt  and  spider- 
webs  to  accumulate.  These  are  easily  blown  off  into  the  air  of  the 
stable  during  milking  and  settle  into  the  milk  pail. 

Storing  the  feed  for  dairy  cows  apart  from  the  milking  stable  and 
placing  it  before  the  cows  at  least  one  hour  before  milking  is  a  means 
of  reducing  the  amount  of  dust  in  the  stable  at  milking  time.     Sprink- 


Fig.  1. — Uncovered  milk  pail.  The 
open-top  pail  is  unsatisfactory  for 
use. 


Fig.  2. — Covered  milk  pail.  The 
hood  may  be  added  to  the  ordinary 
type  of  pail  as  here  shown. 


ling  the  hay  before  placing  it  before  the  cows  is  practiced  by  some 
dairymen  to  keep  down  the  dust  in  the  stable.  Recent  experiments 
at  the  New  York  Agricultural  Experiment  Station  have  shown  that 
the  contamination  of  milk  in  the  stable  from  dust  is  of  less  importance 
than  has  been  believed  in  the  past. 


CLEANSING  OF  UTENSILS 

The  cleanliness  and  proper  care  of  dairy  utensils  can  be  considered 
the  most  important  item  in  producing  milk  with  a  low  bacteria  count. 
Proper  cleansing  of  dairy  utensils,  briefly  described,  consists  in  first 
rinsing  them  in  cold  or  lukewarm  water  to  remove  milk  and  any 
sediment  that  may  be  present,  then  brushing  with  a  washing-solution 


to  thoroughly  clean  them,  followed  by  rinsing  in  warm  water  to  re- 
move the  washing-solution.  The  purpose  of  removing  the  milk  and 
any  sediment  that  may  be  present  in  the  utensils  by  the  first  rinsing 
is  to  keep  the  washing-solution  as  clean  as  possible.  Where  this 
method  of  cleaning  is  not  practiced  dried  milk  is  frequently  found 
clinging  to  dairy  apparatus,  being  baked  upon  the  tinware  from 
scalding  it  before  all  milk  is  removed.  The  washing-solution  will 
become  polluted  with  sand,  flies  and  manure  from  the  bottom  of  the 
milk  pails  if  this  first  rinsing  is  ignored. 


Fig.  3. — Covered  milk  pail  for  use  with  cheese  cloth  and  cotton  strainer  over 
opening.      Milk  is  poured  out  through  spout. 


The  washing-solution  prepared  from  sal  soda  or  from  one  of  the 
commercial  washing  powders  should  be  used  warm  and  with  thorough 
brushing  of  all  surfaces  of  the  milk  containers  and  utensils,  and  should 
dirt  and  other  foreign  material  accumulate  in  it  a  fresh  solution 
should  be  prepared. 

The  third  step  in  cleaning  the  utensils  consists  in  rinsing  with 
clean  warm  water  to  remove  the  washing-solution  and  leave  a  fresh, 
clean  surface  for  the  milk.  Utensils  cleaned  in  this  way  may  still 
contain  thousands  of  bacteria  although  the  number  present  would 
be  much  lower  than  in  poorly-cleaned  utensils.  To  destroy  all 
bacteria  in  utensils  these  must  be  thoroughly  sterilized  with  steam 
or  boiling  water. 


UNSTERILIZED  UTENSILS  THE  GREATEST  SOURCE  OF  BACTERIA 

IN  MILK 

The  greatest  source  of  bacteria  in  milk  is  unsterile  utensils  and 
these  bacteria  are  the  most  important  ones  to  destroy  because  they  are 
accustomed  to  growing  in  milk  and  reproduce  in  it  extremely  fast 
when  milk  is  placed  into  such  containers.  Many  of  the  dust  bacteria 
develop  in  milk  more  slowly  and  some  of  them  perish  in  milk  because 
it  is  not  suitable  for  their  growth  and  reproduction. 

All  dairy  utensils,  including  milk  cooler,  pails,  strainer  cloths, 
milk  cans,  vats  and  bottles  should  either  be  placed  into  a  tightly-closed 
compartment  and  treated  with  live  steam  under  pressure  for  twenty 
minutes  or  boiled  for  twenty  minutes  in  the  type  of  sterilizer  shown 
in  figure  2,  if  every  effort  is  to  be  made  to  lessen  the  number  of 
bacteria  in  milk. 

Strainer  cloths,  after  washing,  should  be  either  spread  out  so  that 
all  parts  of  the  cloth  are  in  direct  contact  with  hot  steam,  or  they 
should  be  boiled.  Unless  they  are  sterilized  thoroughly  by  one 
or  the  other  of  these  methods  they  may  become  the  greatest  source 
of  bacteria  in  milk. 

The  usual  method  of  applying  steam  directly  to  dairy  utensils 
from  a  pipe  or  steam  hose  is  not  effective  although  it  has  been  shown 
that  with  a  boiler  pressure  of  thirty  pounds,  where  the  steam  is 
applied  for  at  least  fifteen  seconds,  most  of  the  bacteria  are  destroyed. 


REDUCING  BACTERIAL  COUNTS  BY  SIMPLE  METHODS 

Although  milk  is  constantly  collecting  bacteria  in  its  journey  from 
the  cow  to  the  consumer  and  in  producing  high-grade  milk  every  step 
in  its  handling  should  be  guarded,  as  already  described,  it  is  still 
possible  to  produce  a  very  satisfactory  quality  of  milk  without  atten- 
tion to  all  of  the  details  heretofore  mentioned  if  extreme  care  is  given 
to  the  sterilization  of  utensils  and  the  milk  is  cooled  as  thoroughly  as 
possible  with  cold  water  and  delivered  within  five  or  six  hours  after  it 
is  produced.  At  the  end  of  this  time  the  milk  must  be  either  pasteur- 
ized or  immediately  cooled  to  50°  F.  and  kept  below  that  temperature; 
otherwise  it  will  deteriorate  rapidly.  This  procedure  is  practical  for 
many  dairymen  producing  market  milk  where  the  milk  is  deliver*  d 
to  city  milk  plants.  Most  distributors  of  milk  in  cities  now  have 
facilities  either  for  pasteurizing  or  cooling  milk  to  a  low  temperature 
so  that  with  thorough  sterilization  of  utensils  by  the  producer  and 
the  early  delivery  of  the  milk  to  the   city  milk  plant  the   bacteria 


7 


content  when  it  reaches  the  distributor  may  be  very  low  as  compared 
with  the  result  when  this  procedure  is  not  carried  out. 

*  8"+ 


$r£/?/L/J?£&  TA/V/C/W  PLACE  OI/£J?  fU&A/ACE— 

Fig.  4. — A  combination  hot-water  heater  and  steam  sterilizer  for  dairy  utensils. 


AN  INEXPENSIVE   STERILIZER 


For  small  dairies  producing  market  milk,  or  for  large  dairies 
shipping  cream,  in  case  a  steam  boiler  is  not  available,  very  satisfac- 
tory sterilization  can  be  accomplished  by  placing  all  dairy  utensils 


8 

into  a  covered  galvanized-iron  tank,  such  as  shown  in  figure  4,  and 
boiling  them  for  twenty  minutes. 

The  sterilizer  tank  may  be  made  of  galvanized  iron  of  any  weight 
or  quality,  but  unless  it  is  constructed  of  heavy  high-purity  galvanized 


'//A 


/As  /i 


Co 


J<? 


*77TT> 


A'/s//////^////////. 


■>H-  $ 


// 


/// 


1*1 

H 

i  i 
i 


//and/e 


Wo''/'  ?"/?* 


\ 


T" 

a" 
k 


/  / 


v'/ 


"A. 


/'>7X<Y////s% 


'///%*  8"-* 


f&ctc@Y~ 


-of- 
<5T£#U/Z£/?  rAA//f  FO&  DA/Pr  LT£/VS/jLS 
—  \S/?ow/r?g  — 
Def&//s  ihr  Co/?$frucf/o/? 
KSccr/ef-  2/r7=lft 

Figure  5 


iron  it  will  soon  burn  out.  Those  made  from  the  best  material  of 
No.  16  or  No.  14  gauge  will  be  the  cheapest  in  the  end  on  account 
of  the  increased  durability,  if  they  are  properly  cared  for.  If  the 
tank  is  made  of  No.  16  gauge  iron  the  top  may  be  only  No.  20 
gauge,  which  will  be  less  expensive  and  just  as  durable  since  the 


cover  is  subjected  to  less  wear  than  the  tank.  Wood  is  the  fuel  most 
commonly  used  in  heating  these  sterilizers  but  in  case  an  oil  burner 
is  used  an  extra  sheet  of  iron  should  be  placed  directly  above  the 
flame ;  otherwise  the  extreme  heat  from  the  oil  burner  will  injure 
the  bottom  of  the  sterilizer  and  decrease  its  durability. 

Since  the  galvanized  iron  usually  carried  by  plumbers  does  not 
exceed  thirty-six  inches  in  width,  the  size  of  sterilizer  cannot  exceed 
that  shown  in  figure  4,  if  it  is  to  be  economically  constructed.  A 
false  bottom  should  be  provided  in  the  bottom  of  the  tank  to  hold  the 
utensils  above  the  boiling  water.  The  heat  from  the  steam  accom- 
plishes the  sterilization  and  by  keeping  the  utensils  above  the  water 
in  the  tank,  they  are  less  likely  to  rust  when  kept  in  the  tank  after 
sterilization. 

The  false  bottom  may  be  constructed  from  *4  x  1  inch  galvanized 
bar  iron,  as  follows : 

Seven  (7)  parallel  pieces  five  inches  apart  to  be  riveted  to  V4  x  1 
inch  end  bars.  The  end  bars  are  turned  downward  at  right  angles 
three  inches  from  each  end  to  form  supports  and  raise  the  false  bottom 
three  inches  from  the  bottom  of  the  tank.  The  metal  frame  is  given 
greater  strength  by  riveting  a  ysxl  inch  angle  iron  through  the  center 
and  parallel  to  the  end  bars.  The  ends  of  this  also  should  be  turned 
at  right  angles  to  rest  against  the  bottom  of  the  tank.  This  size- 
tank  is  sufficient  for  the  sterilization  of  the  cans  and  other  dairy 
utensils  on  dairies  of  the  size  previously  stated.  The  sterilizing  tank 
may  be  filled  twice  with  utensils  in  case  it  is  not  sufficiently  large 
to  allow  for  sterilizing  all  utensils  at  one  time. 


SPECIFICATIONS    FOR    STERILIZING    TANKS    OF    DIFFERENT 
CONSTRUCTION 

I.  One  Sterilizer. — Made  from  high-purity  galvanized  iron.  Width  34VL> 
inches,  length  36  inches,  height  28%  inches.  Body  to  be  made  from  No.  16 
galvanized  iron  and  top  to  be  No.  20  galvanized  iron.  All  seams  to  be  riveted 
and  soldered  to  render  watertight.  Upper  edge  to  be  equipped  with  y±  inch 
wire  around  outside  and  galvanized  iron  folded  over  in  neat  manner.  Cover  to 
be  flanged  down  2  inches  all  around  to  make  the  cover  perfectly  tight.  One  side 
of  tank  to  be  fitted  with  %  inch  faucet  attached  by  means  of  a  %  inch  galvanized 
flange  union.      Sterilizer  to  be  complete,  ready  for  immediate  use. 

II.  One  Sterilizer. — Same  as  I,  except  with  the  f ollowing  changes :  Upper 
edge  to  be  equipped  with  %  x  2  inch  flat  strip  so  as  to  make  the  cover  perfectly 
tight.  Cover  to  be  flanged  down  4  inches  all  around.  (This  sterilizer  will  be 
somewhat  more  expensive  than  I,  but  a  higher  temperature  can  be  maintained 
since  the  cover  can  be  made  to  fit  closer  around  the  edges  and  confine  the  steam 
more  satisfactorily  than  in  the  case  of  I.) 


10 

III.  One  Sterilizer. — Made  from  ordinary  galvanized  iron.  Body  and  top 
to  be  made  from  No.  2-4  gauge  galvanized  iron.  All  edges  to  be  double  seamed 
and  soldered  to  render  watertight.  Upper  edges  to  be  equipped  with  %  inch 
wire  around  outside  and  galvanized  iron  folded  over  in  neat  manner.  Cover  to 
be  flanged  down  1  inch  all  around  to  make  cover  perfectly  tight.  One  side 
of  tank  to  be  fitted  with  %  inch  faucet  attached  by  means  of  a  %  inch  galvanized 
flange  union.      Sterilizer  to  be  complete,  ready  for  immediate  use. 

The  cost  of  galvanized-iron  sterilizing  tanks  varies  with  the  price 
of  galvanized  iron,  which  at  present  is  higher  than  average.  From 
figures  obtained  in  the  spring  of  1917  the  first  sterilizer  described 
would  cost  about  $22,  the  second  about  $27,  and  the  third  about  $11. 


USE   OF   STERILIZER 

The  sterilizer  may  be  mounted  over  a  brick  or  stone  furnace.  It 
may  be  used,  first,  for  heating  water  for  washing  utensils.  After 
water  is  drawn  off  at  faucet  and  utensils  are  properly  cleaned  they 
can  be  placed  in  the  tank,  which  should  contain  about  two  inches 
of  water,  cover  placed  in  position  and  the  utensils  boiled  for  about 
twenty  minutes.  Sterilizers  of  this  type  are  now  being  used  by  many 
dairymen  supplying  milk  and  cream  to  the  cities  of  Los  Angeles 
and  Seattle,  and  their  use  is  believed  to  have  been  of  material  assist- 
ance in  reducing  the  number  of  bacteria  in  the  milk  from  dairies  in 
those  sections.  After  sterilizing  the  utensils  they  may  be  removed  to 
a  screened  milk  room  and  turned  over  a  draining-rack  to  dry.  The 
sterilizer  will  be  more  durable  if  water  is  drawn  off  and  it  is  allowed 
to  dry  after  each  using. 


EFFECT    OF    TEMPERATURE    AND    AGE    UPON    BACTERIAL    GROWTH 

IN  MILK 

The  temperature  at  which  milk  is  kept  is  the  most  important 
condition  influencing  the  rate  of  growth  of  bacteria. 

The  milk-souring  bacteria  reproduce  most  rapidly  when  milk  is 
held  at  a  temperature  of  70°  F.  In  order  to  avoid  early  souring  of 
milk  and  its  rapid  deterioration  it  must  be  held  at  a  low  temperature 
even  though  it  lias  been  produced  in  a  clean  manner. 

Most  bacteria  do  not  grow  in  milk  if  it  is  kept  below  a  temperature 
of  40°  F.  In  practical  dairy  work  milk  should  either  be  cooled  as 
low  as  possible  with  cold  water  and  delivered  to  the  consumer  within 
five  or  six  hours  after  it  is  produced,  or  cooled  to  a  temperature  below 
50°  P.  and  stored  at  that  temperature  until  used. 


11 


SUMMARY 

1.  Bacteria  in  milk  originate  from  the  udder,  bod}'  of  the  cow. 
milker,  milking  stable  and  unsterilized  utensils. 

2.  Unsterilized  milk  utensils  are  the  greatest  source  of  bacteria  in 
market  milk. 

3.  The  cooling  of  milk  and  its  age  are  other  important  factors 
influencing  the  bacteria  content  of  milk. 

4.  Ideal  sterilization  of  dairy  apparatus  consists  in  placing  all 
utensils,  strainer  cloths,  bottles,  etc.,  into  a  tightly-closed  compartment 
and  treating  with  live  steam  under  pressure  of  at  least  five  pounds 
for  twenty  minutes. 

5.  An  inexpensive  sterilizing  tank  for  small  dairies  producing 
market  milk  or  large  dairies  shipping  cream  can  be  constructed  from 
heavy  galvanized  iron,  and  mounted  over  a  brick  or  stone  furnace 
where  utensils  should  be  boiled  for  at  least  twenty  minutes. 


STATION   PUBLICATIONS   AVAILABLE   FOR   FREE   DISTRIBUTION 


REPORTS 

1897.     Resistant  Vines,  their  Selection,   Adaptation,   and  Grafting.     Appendix  to  Viticultural 
Report  for  1896. 

1902.  Report  of  the  Agricultural  Experiment  Station  for   1898-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for  1901-03. 

1904.  Twenty-second  Report  of  the  Agricultural  Experiment  Station  for   1903-04. 

1914.  Report  of  the  College  of  Agriculture  and  the  Agricultural  Experiment  Station,   July, 

1913-June,   1914. 

1915.  Report  of  the  College  of  Agriculture  and  the  Agricultural  Experiment   Station,   July, 

1914-June,    1915. 

1916.  Report  of  the  College  of  Agriculture  and  the  Agricultural  Experiment  Station,   July, 

1915-June,   1916. 

1917.  Report  of  the  College  of  Agriculture  and  the   Agricultural   Experiment   Station,   July, 

1916 — June,   1917. 

BULLETINS 


No. 

230. 
241. 
242. 
246. 
248. 

249. 
250. 
251. 


252. 
253. 

255. 
257. 
261. 

262. 

263. 
264. 
265. 
266. 

267. 
268. 


No. 
113. 
114. 
115. 
121. 

124. 
126. 
127. 
128. 
129. 
131. 
133. 
134. 
135. 
136. 
137. 
138. 
139. 


140. 


141. 

142. 

143. 

144. 
145. 

147. 
148. 
150. 
151. 


No. 

Enological  Investigations. _  270. 
Vine  Pruning  in  California,  Part  I. 
Humus  in  California  Soils. 

Vine  Pruning  in  California,  Part  II.  271. 

The  Economic  Value  of  Pacific  Coast  272. 

Kelps.  273. 
Stock-Poisoning  Plants  of  California. 

The  Loquat.  274. 
Utilization  of  the  Nitrogen  and  Organic 

Matter   in    Septic   and    Imhoff   Tank  275. 

Sludges. 

Deterioration  of  Lumber.  276. 

Irrigation   and   Soil   Conditions   in  the  277. 

Sierra  Nevada  Foothills,  California.  278. 

The   Citricola   Scale.  279. 

New  Dosage  Tables.  280. 
Melaxuma    of    the    Walnut,     "Juglans 

regia."  281. 
Citrus   Diseases   of   Florida   and   Cuba 

Compared  with  Those  of  California.  282. 
Size  Grade  for  Ripe  Olives. 

The  Calibration  of  the  Leakage  Meter.  283. 

Cotton  Rot  of  Lemons  in  California.  284. 

A  Spotting  of  Citrus  Fruits  Due  to  the  285. 

Action  of  Oil  Liberated  from  the  Rind.  286. 

Experiments  with  Stocks  for  Citrus.  287. 
Growing  and  Grafting  Olive  Seedlings. 

CIRCULARS 
No. 
152. 


A  Comparison  of  Annual  Cropping,  Bi- 
ennial Cropping,  and  Green  Manures 
on  the  Yield  of  Wheat. 

Feeding  Dairy  Calves  in  California. 

Commercial  Fertilizers. 

Preliminary  Report  on  Kearney  Vine- 
yard Experimental  Drain. 

The  Common  Honey  Bee  as  an  Agent 
in   Prune   Pollination. 

The  Cultivation  of  Belladonna  in  Cali- 
fornia. 

The  Pomegranate. 

Sudan  Grass. 

Grain  Sorghums. 

Irrigation  of  Rice  in  California. 

Irrigation  of  Alfalfa  in  the  Sacramento 
Valley. 

Control  of  the  Pocket  Gophers  in  Cali- 
fornia. 

Trials  with  California  Silage  Crops  for 
Dairy  Cows. 

The  Olive  Insects  of  California. 

Irrigation  of  Alfalfa  in  Imperial  Valley. 

The  Milch  Goat  in  California. 

Commercial  Fertilizers. 

Vinegar  from   Waste   Fruits. 


Correspondence  Courses  in  Agriculture. 

Increasing  the  Dutv  of  Water. 

Grafting  Vinifera  Vineyards. 

Some  Things  the  Prospective  Settler 
Should  Know. 

Alfalfa   Silage  for  Fattening  Steers. 

Spraying  for  the  Grape  Leaf  Hopper. 

House  Fumigation. 

Insecticide  Formulas. 

The  Control  of  Citrus  Insects. 

Spraying  for  Control  of  Walnut  Aphis. 

County  Farm   Adviser. 

Control  of  Raisin   Insects. 

Official  Tests  of  Dairy  Cows. 

Melilotus  Indica. 

Wood  Decay  in  Orchard  Trees. 

The  SUo  in  California  Agriculture. 

The  Generation  of  Hvdrocyanic  Acid 
Gas  in  Fumigation  by  Portable  Ma- 
chines. 

The  Praotical  Application  of  Improved 
Methods  of  Fermentation  in  Califor- 
nia Wineries  during  1913  and  1914. 

Standard  Insecticides  and  Fungicides 
versus  Secret  Preparations. 

Practical  and  Inexpensive  Poultry  Ap- 
pliances. 

Control  of  Grasshoppers  in  Imperial 
Valley. 

Oidium  or  Powderv  Mildew  of  the  Vine. 

SueerrstionR  to  Poultrymen  concerning 
Chicken    Pox. 

Tomato   Crowing  in  California. 

"Lungworms." 

Round  Worms  in   Poultry. 

Feeding  and   Management  of  TTogs. 


Some  Observations  on  the  Bulk  Hand- 
ling of  Grain  in  California. 

Announcement  of  the  California  State 
Dairy  Cow  Competition,    1916-18. 

Irrigation  Practice  in  Growing  Small 
Fruits  in  California. 

Bovine  Tuberculosis. 

How  to  Operate  an  Incubator. 

Control  of  the  Pear  Scab. 

Home  and  Farm  Canning. 

Lettuce    Growing   in    California. 

161.  Potatoes  in   California. 

162.  White    Diarrhoea    and    Coccidiosis    of 

Chicks. 
Small  Fruit  Culture  in  California. 
Fundamentals    of    Sugar    Beet    under 

California  Conditions. 
The  County  Farm  Bureau. 

167.  Feeding  Stuffs  of  Minor  Importance. 

168.  Spraying  for  the  Control  of  Wild  Morn- 
ing-Glory  within  the  Fog  Belt. 

1918  Grain  Crop. 

Fertilizing  California  Soils  for  the  1918 

Crop. 
The  Fertilization  of  Citrus. 
Wheat  Culture. 
The    Construction    of    the    Wood-Hoop 

Silo. 
Farm  Drainage   Methods. 
Progress  Report  on  the  Marketing  and 

Distribution    of    Milk. 
Hog      Cholera      Prevention      and     the 

Serum    Treatment. 
Grain    Sorghum    Seed. 
The   Packing  of  Apples   in   California. 


153. 

154. 

155. 
156. 
157. 
158. 
160. 


164. 
165. 


166. 


169. 
170. 

171. 
172. 
173. 

174. 
175. 

176. 

177. 
178. 


